The present invention relates to an electromagnetic lock. More particularly, the present invention relates to such an electromagnetic lock which is simple in structure, easy and inexpensive to manufacture, and which can be flexibly made in the desired size.
A conventional electromagnetic lock is generally comprised of an electromagnet fastened to a fixed door frame or jamb, and a strike (armature) plate attached to a movable door. The electromagnet is connected to a power supply by a control circuit. Connecting the power supply to the electromagnet causes the door to be locked when closed; disconnecting the power supply from the electromagnet causes the door to be unlocked.
Conventionally, an electromagnet is generally made from hundreds of silicon steel plates which are connected together through the process of welding or by screws, forming into an electromagnetic core. Then, a well-prepared coil is inserted in the electromagnetic core and sealed with a resin. After setting of the resin, the electromagnetic core thus obtained is reprocessed into an electromagnet. An electromagnet made according to the aforesaid manufacturing process may gather rust easily at the connecting areas among the silicon steel plates thereof. Another disadvantage of this electromagnet is its low structural strength. Once it is damaged, its holding force will be greatly reduced. Further, the aforesaid electromagnet manufacturing process will cause environmental pollution problem.